Traumatic brain injury (TBI) is a major public health problem, with over 1.7 million new cases occurring each year in the United States alone. Axons are the cellular components most at risk in TBI. While there is currently no effective treatment for axonal injury in head injured patients, laboratory experiments using rodent models of TBI show the immunosuppressant drugs Cyclosporin-A and FK506 as beneficial in improving the structure and function of axons when applied as treatments following TBI. This project investigates a novel use for the antibiotic Clofazimine (CFZ) as a neuroprotectant to improve outcome following TBI. The research objectives of the project build on exciting new evidence that CFZ improves the properties of compound action potentials (CAPs) evoked in corpus callosum axons, following an experimental TBI in adult rats. CFZ mimics the neuroprotective properties, but lacks the nephrotoxic side effects, of Cyclosporin-A and FK506. In this way it may have more potential as a treatment which may ultimately translate to clinical usage. The goals of this project are to 1) determine the ultrastructural and molecular changes which accompany CFZ benefits observed for evoked axonal CAPs; 2) explore the glial role (microglia, astrocytes, oligodendrocytes) in CFZ neuroprotection; and, 3) investigate the efficacy of CFZ to improve performance in working memory, spatial cognition, and neurological behavior after TBI. The long-term goal is to translate findings from these laboratory studies to the development of therapeutic strategies to improve white matter functioning specifically, and outcome of TBI generally, in human patients.